There are currently 550 unique cases (species x site of action) of herbicide resistant weeds globally, with 276 species (156 dicots and 120 monocots). Weeds have evolved resistance to 21 of the 31 known herbicide sites of action and to 168 different herbicides. Herbicide resistant weeds have been reported in 103 crops in 76 countries. The website has 3519 registered users and 774 weed scientists have contributed new cases of herbicide resistant weeds. View Recent Additions, Site of Action Summary, or the Herbicide Classification System.